In the course of periodontal disease, infection of gingival tissue by plaque bacteria causes the ligaments attaching the gum and teeth to recede, decalcifies the bony structure holding the teeth roots to the bone, and forms periodontal pockets in the gingival tissue adjacent the teeth. Successful periodontal restoration is known to occur if periodontal ligament cells are allowed to colonize root surfaces preferentially over gingival epithelial cells, gingival fibroblasts or osteoblasts. Surgery alone, however, does not result in restoration of lost periodontium.
In an attempt to promote and achieve periodontal restoration, implant techniques have been developed. For example, microporous membranes, such as the Millipore.RTM. filter and GORE-TEX.RTM. membranes, have been developed for use in periodontal tissue regeneration. Typically, the periodontal flap is cut, and the microporous membrane is surgically inserted to cover the surface of the tooth root and to physically occlude epithelial cells from apically migrating along the root surface.
These membranes have several drawbacks. Besides providing variable results, a second surgical entry is needed to remove the membrane after tissue regeneration has been achieved because the membranes are not biodegradable. There is also a higher incidence of infection in connection with their use.
To preclude surgical removal of an implant, membranes made of bioabsorbable material, such as microfibrillar collagen, polylactic acid, and polygalactin (Vicryl.RTM.) mesh have been used. Fitting and positioning these membranes to the implant site is cumbersome and time-consuming, and the therapeutic effect of these membranes has been unpredictable. In addition, the degradation time of membranes composed of collagen has been variable, and the risk of adverse immunological reaction to this foreign protein material in the body presents a major concern.
A liquid system containing a biodegradable polymer has been developed wherein the solution is injected into an implant site, and solidifies in situ to form a biodegradable implant having a solid microporous matrix. Advantageously, the implant does not require surgical removal. However, controlled delivery and containment of a liquid system within a particular area within the implant site is difficult, and the liquid may spread to areas other than the implant site.
Therefore, there is a need for an article which will facilitate the controlled placement in an implant site of a liquid polymer solution for forming an implant. A further need is to develop a precursor to a solid implant which is neither all-liquid nor all-solid but will solidify in situ to form a solid microporous implant. There is also a need for a precursor to a solid implant that can be applied to a tissue defect in an animal and shaped or molded in situ to conform to the defect. Yet another need is to develop in vivo and ex vivo methods of making an implant precursor having such characteristics.